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| - FTIR Investigation of 2-Chlorophenol Chemisorption on a Silica Surface from200 to 500 °C
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| - The time-dependent chemisorption of 2-chlorophenol on a fumed silica surface was studied in situ from 200to 500 °C using a temperature-controlled dosing cell and FTIR absorption spectroscopy. 2-Chlorophenol wasfound to chemisorb at isolated and geminal surface hydroxyl sites. 2-Chlorophenol chemisorption andsubsequent surface oxidation resulted in a mixture of chlorophenolate and partial oxidation products, such asformates and acetates. The rates of chemisorption were measured, and the activation energy of adsorptionwas found to be 15 ± 4 kJ mol-1 for a fast, initial reaction and 22 ± 2 kJ mol-1 for a slower reaction athigher surface coverage. This work was motivated by the observation that combustion-generated fly ashmediates the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) at temperaturesbetween 250 and 450 °C. Although transition metals such as copper are known to catalyze or mediate thisreaction, silica is the major component of fly ash and chemisorption at higher concentration surface sites ofsilica must have a significant impact on the surface-mediated PCDD/F formation on fly ash surfaces.
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